1. Field of the Invention
The present invention relates to a digital camera that controls the emission amount of a flash using face information included in a subject, and a method therefor.
2. Description of the Related Art
Generally, digital cameras initiate image taking before the shutter release button is depressed, and exposure control and focus control are performed using the image obtained during that period. The image obtained during that period is also used for a flash control to obtain an adequate emission amount of a flash. In the past, the method in which the adequate amount of flash is obtained based on the overall brightness of the obtained image has been commonly used. Recently, however, a flash control method in which face detection is performed on the obtained image, and emission amount of the flash is controlled according to existence or nonexistence of a face, or the proportion of the detected face in the image.
For example, U.S. Patent Application Publication No. 20030071908 describes a method in which emission amount of a flash is reduced if a face is detected and the ratio of the face in the image is greater than or equal to a predetermined value. Further, U.S. Patent Application Publication No. 20060044422 describes a method in which emission amount of a flash is obtained using only the image data of a region corresponding to a face in the image, or using image data in which a region corresponding to a face in the image is weighted greater than for the other regions.
Further, when a person is imaged with a flash at night or in a dark place, the eyes of the person may sometimes be imaged in red or gold (hereinafter, collectively referred to as “red eye” including gold and other colors). It is known that the red eye phenomenon occurs when the pupils of the eyes are opened widely. Consequently, some digital cameras have a function to emit a flash to close the pupils to a certain degree prior (hereinafter referred to as “redeye reduction emission”) to performing flash photography, and thereafter performing ordinary flash photography as described, for example, Japanese Unexamined Patent Publication No. 2001-215404.
The methods described in U.S. Patent Application Publication Nos. 20030071908 and 20060044422 may obtain an image of appropriate brightness without halation in the face portion or without the face portion becoming too dark, if the content of image data obtained for face detection is identical to the content of image data obtained for light control. But, the position of a face included in the image data obtained for light control may sometimes differ from the position of the face detected from the image data obtained for face detection, since the face detection is performed prior to exposure control and focus control. In this case, the emission amount obtained based on the data of a region extracted as the region corresponding to the face may not become an optimum amount. Further, a more inadequate emission amount may be set in comparison with a case where the emission amount is obtained without considering the face, depending on an object newly located in the region where the face was detected as a result of the change in the face position.
The aforementioned problem is particularly serious for flash photography involving the redeye reduction emission. The redeye reduction emission is primarily performed for closing the pupils to a certain degree, and the imaging is suspended for a certain time which is required by the pupils to contract in response to the redeye reduction emission, so that it is more likely that the aforementioned problem occurs in comparison with imaging without the redeye reduction emission.
It is an object of the present invention to provide a digital camera capable of invariably performing a flash emission with an appropriate amount by solving the problem arising from the movement of the subject or digital camera during the time frame between the face detection and light control in imaging involving the redeye reduction emission described above.